Abstract 216

Introduction: Persistent pulmonary hypertension (PPHN) is characterized by increased pulmonary vascular resistance, decreased pulmonary blood flow and refractory hypoxia. Inhaled nitric oxide (iNO) improves oxygenation and decreases the need for ECMO. We investigated the effects of nebulized sodium nitroprusside (Neb-NP), a NO donor, and compared these to the effects of iNO in a piglet model of hypoxic pulmonary vasoconstriction.

Method: Newborn piglets (n=5) were anesthetized, mechanically ventilated and instrumented to continuously measure systemic (SAP) and pulmonary (PAP) arterial pressures and cardiac output (CO; electromagnetic flow transducers). Hypoxia was induced (FiO2 0.14). After cardiovascular variables reached a new equilibrium, treatment with either Neb-NP (5 mg/ml @ 4L/min flow) or iNO (20 ppm) was begun. Treatment was randomly assigned. After equilibrium, measurements were recorded. Between treatments, piglets recovered in FiO2 0.50. Hypoxia was again induced, the other treatment instituted and measurements recorded.

Results: Hypoxia prior to treatment was similar between groups (PaO2 = 31.6±3.7(sem) torr prior to Neb-NP and 29.2±2.5 torr prior to iNO). PAP elevation following hypoxia was also similar (Neb-NP: 18 to 33 mmHg; iNO: 18 to 32 mmHg). SAP and CO were not significantly altered by hypoxia in either group. Neb-NP during hypoxia significantly reduced PAP (from 33 ±1 to 23 ±2 mmHg; p<0.01), without significantly altering SAP (91 to 87 mmHg) or CO (918 to 848 ml/min). Inhaled NO also significantly reduced PAP (from 32 ±2 to 21 ±1 mmHg; p<0.01) without significantly changing SAP (96 to 91 mmHg) or CO (861 to 833 ml/min). The decrease in PAP following Neb-NP (9.2±0.9 mmHg; p=0.0004) was comparable to the decrease in PAP following iNO (11.0± 1.1 mmHg; p=0.0006).

Conclusions: 1) Neb-NP significantly ameliorated pulmonary hypertension in a piglet model of hypoxic pulmonary vasoconstriction.

2) The effects of Neb-NP were comparable to iNO.

3) Neb-NP may be a useful adjunct to inhaled NO in conditions associated with PPHN. (Figure)

Fig 1
figure 1

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